.223 Rem - 77gr Sierra Match King with VihtaVuori N540

Published on May 11, 2018
Duration: 24:10

This video details the ongoing quest to replicate the performance of Black Hills' 77gr OTM Mark 262 Mod 1 ammunition. The instructor meticulously tests VihtaVuori N540 powder with 77gr Sierra Match King bullets in .223 Remington, focusing on achieving specific muzzle velocities (2750-2760 fps) and sub-MOA accuracy without pressure signs. The content includes detailed load development, chronograph readings, and group analysis, offering valuable insights for advanced reloaders and precision shooters.

Quick Summary

The quest to clone Black Hills' 77gr OTM Mark 262 Mod 1 ammunition focuses on achieving 2750-2760 fps and sub-MOA accuracy without pressure signs. VihtaVuori N540 powder with 77gr Sierra Match King bullets showed excellent promise, delivering tight groups and high velocities, making it a strong candidate for this precision reloading project.

Chapters

  1. 00:00Introduction: Mark 262 Mod 1 Clone Goal
  2. 00:36Performance Metrics: Velocity, Accuracy, Pressure
  3. 01:01Powder Testing History
  4. 01:33Upper Receiver Configuration Change
  5. 02:28Initial Verification Loads
  6. 02:54Load Data: Accurate 25 20, 8208 XBR, AR Comp
  7. 03:47Introducing VihtaVuori N540
  8. 04:27Brass and Primer Selection
  9. 04:42Overall Length (OAL) Target
  10. 05:18Powder Weighing and Bullet Seating
  11. 06:10Applying a Crimp
  12. 06:35Vihtavuori N540 Case Fill and Expectations
  13. 07:34Seating Compressed Loads with N540
  14. 09:56Sighting In and Chronograph Setup
  15. 10:42Shooting Conditions and Setup
  16. 10:46Accurate 25 20 Group Results
  17. 11:44Analysis of Accurate 25 20 Performance
  18. 12:138208 XBR Group Results
  19. 13:13AR Comp Group Results
  20. 13:55VihtaVuori N540 Load Development Begins
  21. 14:01N540: 24.1 Grains
  22. 15:02N540: 24.4 Grains
  23. 16:15N540: 24.7 Grains
  24. 16:29N540: 25.0 Grains
  25. 17:18N540: 25.3 Grains (Max Charge)
  26. 18:02Brass Inspection Post-Firing
  27. 18:51Group Analysis: Accurate 25 20
  28. 19:34Group Analysis: 8208 XBR
  29. 19:47Group Analysis: AR Comp
  30. 20:03Group Analysis: VihtaVuori N540 (Initial)
  31. 20:23Group Analysis: VihtaVuori N540 (Compressed Charges)
  32. 20:58Overall Results and Future Plans
  33. 21:02Comparison to 224 Valkyrie and AR10 Projects
  34. 21:55Next Episode Preview: Alliant Power Pro Varmint
  35. 23:09Other Powders to Test
  36. 23:58Conclusion and Wrap-up

Frequently Asked Questions

What is the primary goal of the Mark 262 Mod 1 clone project?

The primary goal is to replicate the performance of Black Hills' 77gr OTM Mark 262 Mod 1 ammunition. This involves achieving a muzzle velocity of 2750-2760 fps and accuracy between 0.5-0.7 MOA from an 18-inch barrel, all while avoiding any pressure signs on the brass.

Which powder showed the most promise for the Mark 262 clone in this video?

VihtaVuori N540 demonstrated significant promise, producing excellent groups as small as 0.461 inches with 24.7 grains of powder, achieving velocities of 2736 fps. While higher compressed charges led to slightly larger groups and minor ejector marks, N540 is considered a strong candidate.

What are the key components used in the reloaded .223 Remington ammunition?

The reloads utilize 77gr Sierra Match King bullets, VihtaVuori N540 powder, twice-fired Lake City brass, and CCI No. 41 primers. The target overall length (OAL) is approximately 2.246 inches.

How does ambient temperature affect chronograph readings and velocity?

Higher ambient temperatures can lead to increased powder burn rate and thus higher muzzle velocities. The video notes that testing at 80 degrees Fahrenheit resulted in higher velocities compared to testing at 50 degrees Fahrenheit, and the Caldwell chronograph also reads higher than a MagnetoSpeed.

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